As a chiller or a heat-pump chiller that requires an ability to handle a relatively large capacity, such as for chilled-water supply in a semiconductor manufacturing plant or local heating and cooling, a turbo chiller (heat source apparatus) that compresses a refrigerant by using a turbo compressor is widely used. A turbo compressor in such a turbo chiller is generally electrically driven by an electric motor, and a known type of electric turbo compressor with an arbitrarily variable rotation speed is equipped with an inverter device.
An inverter device used in such an electric turbo compressor with a variable rotation speed is equipped with a power device, such as an insulated gate bipolar transistor (referred to as “IGBT” hereinafter), and a large current flows into the power device in accordance with the torque required by the electric motor.
To protect the power device in the case where an excessive current flows therein, the inverter device is provided with an overcurrent protective function that stops the inverter device when an overcurrent flows therein, as described in Patent Document 1. This overcurrent protection is performed by an inverter control portion, such as a microcomputer, provided in the inverter device, which is independent of a control device of an air conditioning apparatus.    Patent Document 1:    Japanese Unexamined Patent Application, Publication No. 2004-32906 (Paragraphs [0018] to [0020] and [0032] to [0045], and FIGS. 1 and 3)